Magnetically energized removable indicating device for vacuum switches



March 15, 1966 H. M. PFLANZ 3,240,909

MAGNETICALLY ENERGIZED REMOVABLE INDICATING' DEVICE FOR VACUUM SWITCHES Filed Oct. 16, 1963 g 40 J7 J0 mag;

-Qikkmwa United States Patent 0 3,240,909 MAGNETICALLY ENERGIZED REMSVABLE IN- DHCATING DEVICE FOR VACUUM WITCHES Herbert M. Pflanz, Roslindale, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed (Pct. 16, 1963, Ser. No. 316,714 4 Claims. (Cl. 200-444) This invention relates generally to electrical indicating means and, particularly, to an indicating device which is especially adapted for use with switches, such as vacuum switches or interruptors, to indicate in response to current flow through such switches whether the contacts thereof are open or closed.

Vacuum switches which, for example, are employed to switch capacitor banks have a high voltage rating (on the order of 14.4 to 34.5 kv., for example) and handle alternating currents on the order of 50 amperes to 20,000 amperes.

A typical vacuum switch comprises an evacuated envelope having a pair of relatively movable contacts therewithin. Vacuum switches employing glass envelopes are relatively fragile and are usually mounted in a housing which affords support, protection and insulation. If the vacuum switch envelope is made of transparent glass, it is convenient to make the housing, or a portion thereof, of transparent insulating material such as clear acrylic plastic to provide for easy visual inspection of the interior of the vacuum switch.

Presently, mechanical position indicators, responsive to movement of the contact operating linkages, are employed to visually indicate whether the vacuum switch contacts are open or closed. Such indicators are not entirely satisfactory because they give only an indirect indication of contact position in the vacuum switch and, being subject to possible breakage of the linkage, are not absolutely reliable. Therefore, it is desirable to provide new and improved contact position indicating means for vacuum switches and the like.

Accordingly, it is an object of this invention to provide improved visual type contact position indicating means for use with a vacuum switch which are responsive to current flow through the vacuum switch and do not depend for operation on actuation by mechanical linkage, and which are operable over the entire range of current and voltage conditions to which the vacuum switch is subject.

Another object is to provide means of the aforesaid character which when in use with enclosed vacuum switches are completely protected from the natural elements and from physical damage.

Another object is to provide an indicating device of the aforesaid character which is compact, relatively easy to fabricate, inexpensive, extremely reliable in use, and easily replaceable for servicing.

Other objects and advantages of the invention will hereinafter appear.

In accordance with the present invention there is provided a vacuum switch for use with alternating current and having an evacuated envelope with relatively movable contact members disposed therein. Conductive members, which may be integral with or merely electrically connected to the contact members, extend from the envelope. A core made of highly saturable magnetizable material is disposed adjacent one of the conductive members and a secondary winding is inductively coupled to the said one conductive member through the core. In a preferred embodiment the core surrounds one of the conductive members and the secondary winding is wound on the core. An indicating lamp of either the incandescent or neon type is electrically connected to the secondary winding. In a preferred embodiment a lamp socket adapted to receive the lamp is mounted on the core. Thus, when the vacuum switch contacts are closed and alternating electric current passes through the conductive member, a voltage is induced in the secondary winding to cause the indicating lamp to light up. The induced voltage, and with it, the brightness of the lamp depends on the operating level of the magnetizing curve. In order to cover a wide current range with only a small voltage change, the operating level is chosen above the saturation point of the core. Conversely, when the vacuum switch contacts open, current flow ceases and the lamp goes out. In this way, visual indication is given of contact position. The core, winding, lamp socket and lamp comprise a modular indicating device which is Well adapted for use with a vacuum switch which is mounted within a housing which is translucent or has a translucent portion.

The accompanying drawing illustrates several preferred embodiments of the invention but it is to be understood that the embodiments disclosed herein are susceptible of modification with respect to details thereof without departing from the scope of the appended claims.

In the drawing:

FIG. 1 is a cross sectional view of a portion of a vacuum switch employing one embodiment of an electrical indicating device incorporating the present invention;

FIG. 2 is a cross sectional view taken along line II-II of FIG. 1;

FIG. 3 is a diagrammatic showing of the circuitry employed in the device shown in FIGS. 1 and 2;

FIG. 4 is a graph illustrating the electrical characteristic of components employed in the indicating device shown in FIGS. 1, 2 and 3;

FIG. 5 is a showing of another embodiment of the invention; and

FIG. 6 is a diagrammatic showing of the circuitry employed in the embodiment shown in FIG. 5.

Referring to FIG. 1, the numeral 10 designates a portion of a typical vacuum switch comprising an envelope 12 which is sealed at one end by means such as a. cap 14. Envelope 12 is understood to be sealed at its other end in a suitable manner. Vacuum switch 10 further comprises a pair of relatively movable electrical contact members 16 and 18 which are shown in open position. Contact 16, which is in the form of an elongated electrically conductive member, is stationary and is supported by and extends through cap 14. Contact 18 is understood to be adapted for axial movement into and out of engagement with contact 16 in a suitable manner. The adjacent ends of contacts 16 and 18 are surrounded by a shielding device 20.

Means are provided for supporting, protecting and insulating vacuum switch 10. Such means comprise a housing 22 made of electrical insulating material. Housing 22 is understood to be made entirely of translucent insulating material but, if desired, only a portion thereof need be translucent to emit light from an indicating de- 3 vice 24, hereinafter described. Housing 22 is closed at one end by an electrically conductive terminal member or plate 26.

Means are provided to removably secure plate 26 to housing 22. Thus, for example, housing 22 is provided with a flange 28 and plate 26 is secured, as by bolts 30, to a ring 32 disposed on the opposite side of the flange. Taking up on the bolts 30 clamps plate 26 against the end of housing 22. Removal of the bolts 30 permits plate 26 to be removed. A gasket 34 is disposed between plate 26 and the end of housing 22.

Means are provided to connect plate 26 to contact 16 of vacuum switch 10 both to provide an electrical connection therebetween and to afford mechanical support for one end of the vacuum switch. Such means comprise an electrically conductive member or stud 36 on plate 26 and further comprise a member or clamp 38 which is adapted to engage the stud and the projecting end portion of contact 16 of vacuum switch 10. Clamp 38 comprises a pair of oppositely disposed notched members 40 which are disposed on a bolt 42 and biased toward each other by compression springs 44- which are disposed on the bolt. Nuts 46 at each end of bolt 42 will permit the tensioning of the springs 44 to be adjusted.

Prior to assembly, clamp 38 is adjusted so as to be able to fit snugly on the end of contact 16 of vacuum switch 10 and on stud 36 of plate 26. During assembly, clamp 38 is slipped onto the end of contact 16, the indicating device 24, hereinafter described, is slipped onto the clamp, and plate 26 is put into place on the end of housing 22 so that its stud 36 engages the clamp.

Referring to FIGS. 1, 2 and 3, indicating device 24 comprises a saturable core 50 of magnetizable material. Core 50 is adapted both by its construction and placement with respect to the current path through the vacuum switch to be highly saturable, as is hereinafter more fully explained. Thus, core 50 is toroidal in form and adapted to fit around the electrically conductive members which serve as a primary transformer winding, i.e., portions of contact 16 and stud 36 and clamp 38 which connects them. Core 50 may, for example, be wound from a strip of magnetic material and disposed on a bobbin 52 which is adapted to fit snugly on clamp 38.

Indicating device 24 further comprises a secondary winding 54, shown schematically in FIGS. 3 and 6, which is wound on core 50 and understood to be electrically insulated therefrom. Secondary winding 54 is secured in place on core 50 by suitable means, as by winding with adhesive insulating tape or coating with an insulating compound.

Indicating device 24 also comprises a lamp socket 56 which is mechanically supported on core 50 by means of adhesive insulating tape or a coating of insulating compound. Lamp socket 56 is understood to be electrically connected across secondary winding 54. Lamp socket 56 may be of any conventional well-known type and adapted to accommodate a lamp 53 which has a screw type, bayonet or other type of base. Lamp 58 may be of the incandescent or neon type.

If desired, indicating device 24 may be provided with two lamp sockets 56 and 60 and two lamps 58 and 62 therefor connected in parallel with each other across secondary winding 54, as FIGS. and 6 show. This provides for maintenance of a visual indication that the contacts of the vacuum switch are closed even if one of the lamps burns out.

As previously mentioned, a vacuum switch which is in service can be subjected to currents which range from 50 amperes to 20,000 amperes momentary current. Accordingly, core 50 of indicating device 24 must be constructed and disposed with respect to the primary current conductor, i.e., connector assembly 42, so as to be highly saturated. This prevents any undue changes in flux from occurring in core 50 when extremely high currents flow through the vacuum switch which would cause high Voltd age in secondary winding and effect burnout of indicator lamp 58.

FIG. 4 shows a preferred relationship between the voltage output from secondary winding 54 and the current flowing through vacuum switch 10. As the graph shows, when the primary current exceeds about 30 amperes, saturation occurs and the output voltage from secondary winding 54 increases only slightly.

The number of turns (N) required for secondary winding 54 may be determined according to the formula:

E N o AX B where E is the induced voltage, A is the sectional area of the core in square inches, and B is the induction expressed in kilolines per square inch, and is chosen within the saturation range of the core.

Thus, for example, where AB is less than 5 volts for a AI of 20,000 minus 50 amperes=l9,950 amperes, a 10 volt lamp was employed with good results in that it gave sutficient light output for a base voltage of 5 volts.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination, a vacuum switch having an evacuated envelope and a pair of relatively movable contacts mounted within said envelope, a conductive member electrically connected to one of said contacts and disposed outside of said envelope, means including a protective housing within which said vacuum switch is disposed, said housing having a translucent portion, a terminal member at one end of said housing, said terminal member being electrically connected to said conductor, a core of magnetizable material Within said housing and adjacent said conductor and adapted to be magnetically saturated in response to current flow through said conductor, a secondary winding within said housing and inductively coupled to the conductor through said core, and at least one lamp disposed within said housing and connected across said winding, the light from said lamp when illuminated being visible through said translucent portion of said housing.

2. The combination according to claim 1 wherein said core surrounds said conductor and wherein said secondary winding and said lamp are supported on said core.

3. In combination, a vacuum switch having an evacuated envelope and a pair of relatively movable contacts mounted within said envelope, a conductive member electrically connected to one of said contacts and disposed outside of said envelope, means including an open ended housing within which said vacuum switch is disposed, said housing having a translucent portion, an electrically conductive removable terminal member for closing one end of said housing, said terminal member having a stud, an electrically conductive removable connector for engaging said conductive member and said stud, and an indicating device disposed within said housing and removably mounted on said connector, said device comprising a core of magnetizable material surrounding said connector and adapted to be magnetically saturated in response to predetermined current fiow through said connector, a secondary winding supported on and inductively coupled to the conductive member through said core, and at least one lamp support-ed on said core and connected across said winding, the light from said lamp when illuminated being visible through said translucent portion of said housing.

4. In combination, a vacuum switch having an evacuated envelope and a pair of relatively movable contacts mounted within said envelope, a conductive member connected to one of said contacts and disposed outside of said envelope, means including a translucent open ended housing within which said vacuum switch is disposed, an electrically conductive removable terminal member for closing one end of said housing, said terminal member having an inwardly projecting stud, an electrically conductive removable connector for engaging said conductive member and said stud, said connector being adapted to expand outwardly when in such engagement, an indicating device disposed within said housing, said device comprising an insulated toroidal core having an aperture for accommodating said connector and being mechanically held in place thereon by expansion of said connector, a secondary winding on said core and inductively coupled to said connector through said core, and at least one lamp supported on said core and connected across said Winding References Cited by the Examiner UNITED STATES PATENTS Luehring et al. 200144 X Mikos 200144 X Greenwood 200144 Gribble 20087 

1. IN COMBINATION, A VACUUM SWITCH HAVING AN EVACUATED ENVELOPE AND A PAIR OF RELATIVELY MOVABLE CONTACTS MOUNTED WITHIN SAID ENVELOPE, A CONDUCTIVE MEMBER ELECTRICALLY CONNECTED TO ONE OF SAID CONTACTS AND DISPOSED OUTSIDE OF SAID ENVELOPE, MEANS INCLUDING A PROTECTIVE HOUSING WITHIN WHICH SAID VACUUM SWITCH IS DISPOSED, SAID HOUSING HAVING A TRANSLUCENT PORTION, A TERMINAL MEMBER AT ONE END OF SAID HOUSING, SAID TERMINAL MEMBER BEING ELECTRICALLY CONNECTED TO SAID CONDUCTOR, A CORE OF MAGNETIZABLE MATERIAL WITHIN SAID HOUSING AND ADJACENT SAID CONDUCTOR AND ADAPTED TO BE MAGNETICALLY SATURATED IN RESPONSE TO CURRENT FLOW THROUGH SAID CONDUCTOR, A SECONDARY WINDING WITHIN SAID HOUSING AND INDUCTIVELY COUPLED TO THE CONDUCTOR THROUGH SAID CORE, AND AT LEAST ONE LAMP DISPOSE WITHIN SAID HOUSING AND CONNECTED ACROSS SAID WINDING, THE LIGHT FROM SAID LAMP WHEN ILLUMINATED BEING VISIBLE THROUGH SAID TRANSLUCENT PORTION OF SAID HOUSING. 